If you asked a pre-industrial person how in the world it would be possible to source, refine, and distribute enough crude oil to power the modern world they would quote some similarly breathless numbers. It's possible because there's a motivation to do it. Simple as that. If we had a similar level of motivation to sequester our excess carbon we could start planning to do that tomorrow and have it done within a decade or three. You can't sequester all the worlds carbon in one place, just like you don't pull it all out of the ground in one place. Big problems seem less so when you realize that solutions are usually distributed.